The power amplifier plays a vital role in many radar, electronic warfare, and communication systems. Performance of these systems is often largely affected by the efficiency of these power amplifiers. Unfortunately most power amplifiers operate in the linear region where their efficiency is pretty low (e.g., approximately 10˜30%). At such a poor efficiency, most power is wasted and converted into heat, which requires the corresponding system to be cooled for reliable operation. Power amplifiers are most efficient when they are operated at peak output power just below the compression point. For a typical RF/communication system, it is possible to achieve up to approximately 50% efficiency when a device is operating at or around peak output power. However, much of the efficiency is lost when output power is backed off from the peak power due to the higher peak-to-average power ratio (PAPR) waveform of modern RF/communication systems.